System for directing radio waves



Nov. 9, 1948. H. B. DE VORE SYSTEM FOR DIRECTING RADIO WAVES Filed June 9; 1944 v INVENTOR v HENR ELDEVURE 5N El Patented Nov. 9, 1948 ZAEBAM SYSTEM FOR DIRECTING RADIO .WAVES;

Henry B. Devon,- Cranbury; NJJi, assignor td Radiofi'orporation of America; a. corporation:

of Delaware Applicationalunel9yl944, Serial-No. 539,5 i2

10 Claims... (01. 250-3353).

:This inventionvrelates .toa, radio.-system. for propagatingcapbeam of radio waves andlfor direct,- ingxsaid :beam through "a y predetermined angle,

and more :particularlyto asystem; inwhich the energylappliedto awave guide is radiated through a lplurality; of radiating. elements spaced: alongone of the sidesof the waveguide and-in which the phase of; the radiatedenergyis varied-by changing the .effectivewave lengthxof the energy within the guide;

Numerous systemst. have been proposed fordirecting aw: beam; Of". radio-4.. frequency; ener y throughout a predetermined angle. Such systems generallyinvolve directive antennas which are oscillated backand forth or relatively complicated means for varying the phase of. the radiated energy whereby the beam is .directedrthroughout the required angle.

According to the: presentrinvention; the me chanical movement required todirect variablya,

beam of radio frequencyenergyisflsimplified; In

a preferred embodiment of f thei invention; the effective wave length of the energy within a wave guide is varied 'sdthat theenergyzis radiated indifferent phase froma plurality of radiating apera tures disposed along the edge of the waveguide; The phase changes whiohrcorrespondtochanges indirection'of the beam are brought. about byasingle rotatable member which :is disposed along apertures. and in'whichthewaves may :bedirected through a-continuouslyvaried range ofangles.

The invention will be described by referring to the; accompanying: drawings in-which: Figure 1 is anuelevational view-of one embodiment of the invention; Figure z ,isaisectional .view taken along the =li'ne IIf-II of: Figure 1; Figure 3 is anview partly in section taken-along the line III-III of Figure 1;

Figures; and Baresectional views of a wave reflection" reducingzelement of. thewave guide; and

Figuresfi and? lareend views ofemodifications of? the 'rotatablecylindrical. member of Fig.1..

Referringzto Figure :1; a vrectangularwa e id l is connected to -a: source of radio frequency energy which is to. be applied to thewave guide. The wave guide l is suitably coupled to a wave guide section 3. The wave guide section 3 is terminated in a wave guide section 5 in which a Wedge l of suitable material is insertedto mini-. mize wave reflections. The details of the'reflection'minimizing means are more clearly'illustrated in Figures 4 and 5.

The central portion of the wave guide. includes a plurality of apertures 9 which terminate irr'the wave .guide opening ll jthrough' smaller apertures 43; The size of the smaller aperture 13 is chosen in accordance withthe desired characteristics of the radiated beam. For example, inone preferred form of the invention the apertures are, made increasing .in sizesuch that the same percentage of. the initial wave .energyis radiated as the wave is propagated from the beginning of the wave guide 3 to its termination in elements 5, If This gives the sharpest possible beam. In another form of the inventiom'the apertures near the center of the wave guide are made larger soas;

to radiate more energy than those at the ends of the wave guide, .so:.that-the distribution of radiated energy across the beam is such as to give, from knownn-antennaatheory; a.principal.; beam nearly free from side lobes... The. apertures preferablyinclude'a..dielectric-member lfiwhich is designed to increase the efiective wave length which will be passed by the apertures 9 to avoid the attenuation which would take-place if the cut-off frequency of the apertures 9 were unchanged.

One side 'of the wave guidemember 3 is open sothat it is adapted to-receive the rotatable cylinderrl'll The rotatable cylinder-includesa-plura-lity of parallel grooves or channels I 9. The efi'ective depth-of the grooves varies from zero to nearly: one quarter of theapplied wave length. The width of the-grooves is preferablydess than one: quarter-of the-wave length'of the appliedenergy. The grooves are spaced preferably-less than onequarter of the wave length. The outer surface of. the rotatable cylinder I1 is journalled in the side walls 2! of the wave guiding member 3 a which is shaped toreceiveth'e rotatable cylinder. A pair ofnuarter wave slots 23 aremachined in the sidewalls 2| to increase the effectiveness with whichhtherotatable member closes off the open s otthe wave guide.

In the operation of: the system, the rotatable cylinder I? is preferably connected to a motor such as 25;.which'rotates the cylinder soas to deflect rthe :beamof .radio waves mat the: desired: 1

frequency. While the energy applied through the wave guide I is of constant frequency, its effective wave length is varied by the change in the wage guide brought about by the change in the depth of the grooves it. As the depth of the grooves changes, the wave length changes, so that the relative phases of the waves radiated through successive openings l3 and apertures 9 changes. The change in phase is progressive as the wave proceeds throughout the wave guiding member 3. Thus the resulting wave front forms an angle with respect to the line through the apertures 9. In this manner the energy radiating through the apertures 9 forms a beam which is oscillated back and forth through a predetermined angle. Choice of suitable dimensions for this system is determined by the following considerations. If the radiating apertures are spaced at a uniform distance d apart, the waves radiated from the separate apertures will reenforce in such a way as to form a beam of radiation inclined at an angle to the normal to the wave guide length such that sin i d 0- 1) where M is the wave length of the radiation in free space and )\g is the effective wave length in the wave guide. )\g in turn is determined by the dimensions of the wave guide and of the grooves in the rotating cylinder. An exact expression is very diflicult to evaluate. An approximation, valid for the case of a wide Wave guide and for a grooved cylinderhaving large radius may be obtained as follows: If the spacing between the smooth wall of the wave guide and the rooved surface opposite is X, the depth of grooves is L, and the ratio of groove width to the center spacing of the grooves is R, then the wave length A in the guide will be where and k2 is determined by the equation:

27rL L x0 x E75 2 In the specific example of Fig. 2 the bottom of the groove [9 is circular and is tangent with the rotatable cylinder IT. In this arrangement, the resulting beam is directed back and forth at a non-uniform rate through two sweeps for each rotation of the cylinder at a uniform rate. It should be understood that the sweep rate may be made uniform by a suitable variation in the groove depth. The beam may be made to sweep once per rotation of the grooved cylinder by arranging the grooves in the form of a plurality of single turn spirals 2'1 of the type shown in Fig. 6. Moreover, the beam may be deflected stepwise into two or more positions by rotating continuously a'cylinder grooved as indicated by the channels 29 in Fig. 7.

While the invention has been described with particular reference to its use and operation as a transmitter, the system may be used for retan X) tanh (kzX) ception'or for both transmission and reception. F

. predetermined angle It should be understood that the claims are intended to either system and eitheruse.

I claim as my invention:

1. A system for propagating a beam of radio waves and for directing said beam through a predetermined angle including a wave guide having a plurality of radiating elements and having an open side, means for applying radio frequency energy to one end of said wave guide; and a, rotatable member, including a plurality of grooves, disposed along said Wave guide to close its open side and to alter the effective wave length of the energy within said guide as a function of the depth of said grooves.

2. A system for propagating a beam of radio waves and for directing said beam through a predetermined angle including a wave guide having a plurality of apertures of different openings and having an open side, means for applying radio frequency energy to one end of said wave guide; and a rotatable member, including a plurality of grooves, disposed along said wave guide to close its open side and to alter the effective wave length of the energy within said guide as a function of the depth of said grooves.

'3. A system for propagating a beam of radio waves and for directing said beam through a predetermined angle including a wave guide having a plurality of apertures of different openings and having an open side, means for decreasing the effective cutoff frequency of said openings, means for applying radio frequency energy to one end of said wave guide; and a rotatable member, including a plurality of grooves, disposed alon said wave guide to close its open side and to alter the effective wave length of the energy within said guide as a function of the depth of said grooves.

4. A system for propagating a beam of radio waves and for directing said beam through 2.

including a wave guide having a plurality of apertures of different openings and having an open side, means for applying radio frequency energy to one end of said wave guide; a rotatable member, including a plurality of grooves, disposed along said wave guide to close its open side and to alter the effective wave length of the energy within said guide as a function of the depth of said grooves; and means for minimizing the reflections from the other end of said Wave guide.

5. A system for propagating a beam of radio Waves and for directing said beam through a predetermined angle including a wave guide having a plurality of radiating elements and having an open side, means for applying radio frequency energy to one end of said Wave guide; a rotatable member, including a plurality of grooves, disposed along said wave guide to close its open side and to alter the effective wave length of the energy within said guide as a function of the depth of said grooves; and means for minimizing the reflections from the other end of said wave guide.

6. A system for propagating a beam of radio Waves and for directing said beam through a predetermined angle including a wave guide having a plurality of apertures of different openings and having an open side, means for decreasing the effective cut-off frequency of said openings, means .for applying radio frequency energy to one end of said wave guide; a rotatable member, including a plurality of grooves, disposed along said wave guide to close its open side and to alter the effective wave length of the energy within said guide as a function of the depth of said groovesj and means for minimizing the refiec- I tions from the other end of said wave guide.

'7. A system for propagating a beam of radio waves and for directing said beam through a predetermined angle including a wave guide, said Wave guide including a plurality of openings and a plurality of radiating elements and having an open side, means for decreasing the effective cutoff frequency of said openings, means for applying radio frequency energy to one end of said Wave guide; a rotatable member, including a plurality of grooves, disposed along said wave guide to close its open side and to alter the effective Wave length of the energy within said guide as a function of the depth of said grooves; and means for minimizing the reflections from the other end of said Wave guide.

8. A system for propagating a beam of radio waves and for directing said beam through a predetermined angle including a Wave guide having a plurality of radiating apertures of different openings and having an open side normal to the plane of polarization of the radiation passing through said Wave guide, dielectric means for increasing the effective cut-off valve length of said apertures, means for applying radio frequency energy to one end of said wave guide, a rotatable cylindrical member disposed to close substantially the open side of said wave guide and including a plurality of parallel circumferential grooves having depths varying from zero to nearly one quarter of the applied wave length and having Widths less than one quarter of the applied wave length whereby said grooves are exposed to said applied radio frequency energy to alter its effective Wave length as a function of said groove depth, and means for minimizing the leakage of energy between said guide and said rotatable means.

9. A system for propagating a beam of radio Number waves and for directing said beam through a predetermined angle including a wave guide having a plurality of radiating elements and having an open side normal to the plane ofpolarization of the radiation passing through said wave guide, means for applying radio frequency energy to one end of said wave guide, a rotatable cylindrical member disposed to close substantially the open side of said wave guide and including a plurality of parallel channels disposed in portions of the cylindrical member defined by radial planes and having predetermined radial depths whereby said channels are exposed to said applied radio frequency energy to alter its effective wave length as a function of said groove depth, and means for minimizing the leakage of energy between said guide and said rotatable means.

10. A system according to claim 8 in which the said grooves are of substantially spiral form.

HENRY B. DE VORE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Buckley Apr. 22, 1919 Heising Nov. 24, 1925 Newhouse July 1, 1941 Southworth July 9, 1940 FOREIGN PATENTS Country Date Australia June 22, 1936 Number 

